The two-judge bench at the Sindh High Court restrained the Pakistan Atomic Energy Commission (PAEC) on Thursday to carry out work at the proposed sites in the southern port city of Karachi without adhering to environmental laws.

The court directive was issued on a petition challenging the environmental impact assessment (EIA) report of the Sindh Environmental Protection Agency which approved the two plants.

The counsel of petitioner said that the reactors would be built by the China National Nuclear Corporation on a design known as ACP-1000 that has not been operational even in China.

"The ACP-1000 reactor so far exists only on paper and in computer program and any real life experience, tests and trials ... on the ACP-1000 design will be from operating the reactors in Karachi," the counsel added.

Karachi, one of the world's most densely populated cities with an estimated population of about 21 million, lacked the infrastructure for mass evacuation of its inhabitants in the wake of a possible nuclear accident, he added.

Pakistan government had finalized plans for starting work on two nuclear power plants of 11,00 MW each — adjacent to the Karachi Nuclear Power Plant - with support from China.

Besides, subsequent plans for two more plants — K-4 and K-5 — were also under consideration.